In conventional medical diagnostic X-ray radiography, an X-ray source and a collimator are suspended from a ceiling by an extending column. The extending column is often referred to as an overhead tube suspension system. The X-ray source sends a beam of X-rays from the X-ray source behind the patient, through the patient's chest, to the recording medium (e.g. film or digital recording means). A collimator is a diaphragm or system of diaphragms made of an absorbing material, designed to define and restrict the dimensions and direction of a beam of radiation from the X-ray source.
The extending column is mounted to carriages to provide freedom of motion that allows general positioning of the X-ray source at the desired location and orientation within an X-ray examination room. In conventional extending columns, the extending column consists of a series of concentric cylinders, either circular or prismatic (e.g. octagonal), with ball bearing assemblies running in channels or on tracks in at least two planes to provide smooth motion with as little free play as possible. In one embodiment, the ball bearing assemblies are on opposing sides of the concentric cylinder. The amount of free play in the extending column is minimized by closely controlling tolerances, and also by providing adjustment means to reduce the clearance for the bearings as much as possible. Conventional extending columns are approximately symmetrical, with guiding and synchronizing means being distributed approximately equally in 2, 3, or 4 sides of the columns.
One problem with conventional extending columns is that the precision of motion is poor, since it is very difficult to manufacture the telescoping sections precisely enough to maintain the parallelism and straightness required among the various column sections thus employed.
Another problem is that that adjustment of the bearings is difficult, and this leads to inconsistencies in moving efforts and stiffness, as well as lost motion in the assemblies.
Yet another problem is that synchronized motion of the column sections is achieved through the use of “J-bars” and the like, which are long bars extending from one section into the next. These J-bars often rub against the sections, which increases friction in movement, which in turn increases wear of the extending column and requires a greater manual force by an operator of the X-ray equipment to position the X-ray source and the collimator mounted on the extending column.
Still yet another problem is that the length of travel permissible for a given column length is limited, because the bearings are not stiff enough if spaced close together. As a result, clinical usage is somewhat restricted, and extensions are sometimes employed to achieve the desired anatomical coverage range.
A further problem is the size of the conventional extending columns. The area close to an X-ray examination table has rather close quarters for the operators of the X-ray equipment. Reducing the size of the extending column would provide more room for the operators.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for an extending column for medical diagnostic that has improved precision of motion. There is also a need for reducing inconsistencies in moving efforts and stiffness, as well as reducing lost motion in the assemblies. There is an additional need to reduce the rubbing of J-bars against sections. There is a further need increase rigidity in order to improve clinical usage without the need for extensions to achieve the desired anatomical coverage range. There is also a need to reduce the size of the extending column.